Thermal time delay relay



Feb. 23, 1943. R C- 'WINANS 2,311,80

THERMAL TIME DELAY RELAY Filed July l1, 1941 /N VEN To@ R. C. W/NANS TTORNEV Patented Feb. 23, 1943 UNITED sTATEs PATENT OFFICE y 2,311.80;- THERMAL TIME DELAY RELAY Robert c. Winans, Chatham, N.- J., assigner to neu Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 11, 1941,-Serlal No. 401,965

claims. (ci. zoo- 122) This invention relates to switching devices and,

more particularly, to relays of the thermal vacuum type. In the control of electrical circuits it is often desirable to delay the opening or closing of such circuits for certain required intervals. It is a well-known expedient to render a relay slow to operate or slow to release by providing a shortcircuited winding on its core whereby the relay amature is delayed in its movement, thereby delaying the closure or opening of the work circuit over the contact springs operated by the armature. For the measurement of short delay intervals this type of relay structure has been found to be very satisfactory. When, however, longer delay intervals are to `be measured, such as intervals of several minutes, this type of relay is not adequate. some of which have been'of the thermal type, `have heretofore been devised which permit longer delay intervals to be attained with a measure of accuracy but they have been complex in structure and, therefore, expensive to manufacture and to maintain.

It is, therefore, the object of the present invention to simplify delay relays of the thermal type and to render such relays more stable in operation and less affected by ambient temperatures.

Other types of delay relays,

elements could be so arranged as to have their contacts normally in engagement and movable l out of engagement by the transfer of heat from p disclose the structural details;

Fig. 2 is a cross-sectional view through the heater assembly of the relay;

Fig. 3 is a top plan view of the heater assembly; and

Fig. 4 shows a modified form of the invention.

The relay comprises a base portion i having four terminal plugs 2 of the usual type insulated- To attainthese objects the relay in accordance with the present invention comprises anl evacuated glass envelope through the press of which extend four lead-in wires, the outer ends of which are connected to the -base terminalv cooperating contacts are secured. 'I'he lower end of one of vthese elements is connected by a short wire to the tubular shield and` serves bothto support. the shield and the enclosed ceramic insulator and to conduct heat from the shield to such bimetallic element. The bimetallic elements may be so positioned as to be normally out-of i contact and to be brought into contact by heat Atransferred from the illamentthrough the ceramic insulator and shield to the adjacent bimetallic element. The other bimetallic element serves as a substantially fixed front contact sup- DOrt and moves toward or away from therst element only-in response to ambient temperatures. If desired, the two' contact supporting ly supported therein. Secured to the base I is a,

glass envelope 3 provided with an inwardly projecting stein 4 in the press of which are sealed four supporting and lead-in wires 5, 6, 7 and 8. The outer ends of the lead-in wires are soldered or otherwise secured to the four terminal plugs 2, respectively. Secured to'the inner or upper end of the lead-in wires 'I and 8 are two bimetallic thermostatic elements 9 and I0, respectively. These elements are positioned parallel to each other and carry contacts upon their upper or free ends which cooperate with each othe1` but which are normally out of engagement.

Secured to the element 9 near its point of support on the lead-in wire 'I is a short wire II the other end of which is secured to the lower, end of a cylindrical metal shield I2. The shield I2 surrounds a cylindrical 'insulator I3, preferably -of ceramic material, which is held within the shield by the lower inturned edge I4 of the shield.

The insulator I3 is provided'iwth two holes I'5 extending,longitudinally therein through which a lament wire IB is looped. The ends of the iilament wire are suitably attached to the upper ends'of the lead-in wires 5 and E.

The wire II extending between the bimetallic element 9 and the shield I2 serves a dual purpose, first as a support for `the heater assembly comprising shield I2, insulator I3 and filament I6, and secondly, as means for conducting heat from the shield to the element 9.

After the elements of the relay have been assembled -the -relay is placed on an evacuating pump station, a baking oven is lowered over the relay and the relay baked for one minute at a temperature of approximately 450 C. to degas the envelope. This short application of heat is ing the metal elements of the relay. The eny velope is then rapidly exhausted. the

pumping `the envelope may be baked for two other one-minute periods to furtherfreeit of gas, so that upon the completion of the pumping thee'nvelope will be entirely free of gas. During this' treatment the lament is also glowed. It is essential that the baking shall not be done continuously at a high temperature .as the bimetallic elements might otherwise take a permanent set and thus render the relay inoperative.

When the larnent i6, in series with a resist-- ance'in the order of i400 ohms, is connected to a 48-volt circuit the lament will start to heat and due to .the ceramic insulator i3 through which the filament is looped such heat will be delayedin reaching the shield I2. The shield i2 as it becomes heated will transfer some of its heat by radiation and some of its heat by conduction over the'wire I i to the bimetallic element 9. Most of the heat, however, is transferred by v conduction. In response tothe transfer of heat the element Si bends toward the element lo and after a predetermined interval following the closure of the filament circuit will engage the element iii to complete a work circuit. This interval may oe made to range between four minutes' and two minutes for voltages between 45' and 50 volts.

By the provision-of a birnetallic element i@ as a support for the frontcontact of the relay, a

fairly uniform contact gap is maintained irrespective of changes in room temperature. llt will, of course, be obvious, as disclosed in Fig.

4, that the element i@ could be provided with a U-shaped extension il at the upper end thereof to embrace the upper end of the element il, and provided with a contact on the downwardly extending free arm of such extension for normal engagement with a contact carriedby the elel ment El, thereby providing normally closed con-^ .tacts separable a predetermined interval follow- Furthermore, the ceramic insulator i3 ,suihcient to degas the envelope Without overlleatv aerraoi '1. 1n a thermal time delay relay, a contact support of bimetallic construction, a second contact support, cooperating contacts on said supports, a heater coil, a shield surrounding said coil ancl'insulated therefrom, and a heat-conducting support for said shield connected between saidA shield and the adjacent one of said supports.

tion, cooperating contacts on said supports, a

heater lament, a shield surrounding said filament and insulated therefrom, a heat-conducting support for said shield connected between said shield and the adjacent one of saidjsupports, and an evacuated envelope surrounding the aforementioned elements.

e. In a thermal time delay relay, an evacuated glass envelope having a tubular stem extending therein through the press of'which four lead-in wires are sealed, twoparallelly disposed contact supports of bimetallic construction secured to the inner ends of two of said lead-in wires, cooperating contacts on the free ends of said supports, a heater filament the ends of which a e connected to the other two of said lead-in wires, a cylindrical metal shield surrounding said lamentand insulated therefrom, and a heat-conducting support for said shield connected between said shield and the adjacent one of said supports.

5. In a thermal time delay relay, an evacuated glass envelope having a tubular stern extending therein through the press of which four lead-in wires are sealed, two parallelly disposed Contact supports of bimetallic construction secured to the inner ends of two of saidflead-in wires, cooperating contacts on the free ends of said supports, a cylindrical metal shield, a heat-conducting support for said shield :connected between said shield and the adjacent one of said supports, a cylindrical 'ceramic insulator supported in said shield and having longitudinally extending holes therethrough, and a filament the ends of which are connected to the other two or" said lead-in l wires looped through the holes of said insulator. i

ROBERT c. v/INANS 

